Single-channel comprehensive protection circuit

ABSTRACT

The present invention discloses a single-channel comprehensive protection circuit of a self-excitation half-bridge series resonant circuit having a single lamp output, including a DC block capacitor C 3 , a first partial pressure resistor R 1 , a second partial pressure resistor R 2 , a rectifying diode D 1 , a filter and integral capacitor C 4 , a release resistor R 3 , a diac D 2 , a filter capacitor C 5 , a filter resistor R 4 , wherein the method of one point of loading point A at the fluorescent lamp filament is used. The present invention normalizes the treatment of abnormal signals for over-current, over-voltage and end of lamp life state etc. in order to replace the conventional design of multi-channel and multi-point sampling for simplifying the circuit, reducing the cost and space, increasing reliability, and facilitating miniaturization development of the electronic lighting products. The present invention can be applied in the self-excitation half-bridge series resonant circuit of a single-lamp, the self-excitation half-bridge series resonant circuit of the multi-lamps, the separate-excitation half-bridge series resonant circuit of a single-lamp and the separate-excitation half-bridge series resonant circuit of the multi-lamp.

FIELD OF THE INVENTION

The invention relates to the abnormality protection technology in theelectric power, electronic and lighting electronic fields, and inparticular to an abnormality protection circuit for an electronicballast used in a fluorescent lamp.

DESCRIPTION OF THE RELATED ART

In the conventional technology field of electronic ballast, amulti-channel protection circuit is generally used to prevent theelectronic ballast from being damaged, when a fluorescent lamp tube isin abnormal conditions, such as over-current, over-voltage, or reachesthe end of lamp life, in order to increase the reliability of productsand extend the service life of the products.

Conventionally, the abnormal signal of over-current is obtained byserially connected resistors in the main loop of the electronic ballastor by the auxiliary winding of the resonant inductance in the lampoutput circuit. When the electronic ballast is overload or when thefluorescent lamp tube leaks or is not activated, the increased currentof the main circuit is obtained by the serially connected resistors inthe main loop or the auxiliary winding of the resonant inductance. Thenthe oscillatory output of the circuit shall be stopped for protectionpurposes. The abnormal signal of over-voltage may be obtained bydetecting the voltage of two ends of a lamp tube. When the electronicpowder of two ends electric poles of the lamp tube starts to age or thelamp tube leaks slowly, the lamp voltage increases under the conditionof the basically invariable lamp current, which makes the lamp powergradually increase. This signal will activate the protection executioncircuit by a rectified DC voltage. The rectification state (EOL) of alamp tube may be obtained from two ends of a feed-through capacitorconnected with the lamp tube. When the electronic powder of two ends ofthe electric poles of the lamp tube ages and becomes asymmetry, therectification effect can appear in the lamp voltage. This signalactivates the protection execution circuit by means of the logical levelobtained by a window comparator or other circuits.

In the conventional technology (see FIG. 1), although the productreliability can be increased by using a multi-channel protectioncircuit, the technical design of the multi-channel protection circuitalso brings the following drawbacks: 1. The integral reliability isreduced due to its complex circuits; 2. The cost increases due to itscomplex circuits; 3. The efforts to minimize product is affected due toits complex circuits and additional components.

SUMMARY OF THE INVENTION

The present invention is provided to solve the problems of reducedreliability, increased cost and volume etc., caused by the multi-channeldetection protection circuit used in conventional technology. Throughthe signal sampling treatment at the same point, the detection andcontrol for over-current, over-voltage and rectification state signal ofthe lamp can be achieved at the same time in order to increase thereliability, reduce cost and the volume of products.

The new technical solution to solve the above-mentioned problems is asingle-channel comprehensive protection circuit of self-excitationhalf-bridge series resonant circuit having a single-lamp output,including a DC block capacitor C₃, a first partial pressure resistor R₁,a second partial pressure resistor R₂, a rectifying diode D₁, a filterand integral capacitor C₄, a release resistor R₃, a diac D₂, a filtercapacitor C₅, a filter resistor R₄, a thyristor SCR, a clamping diode D₃and a control winding T_(1D); characterized in that one end of the DCblock capacitor C₃ is connected with the first partial pressure resistorR₁, and the other end of the DC block capacitor is connected with aloading point A of one end of a fluorescent lamp filament; the other endof the filament is connected with a resonant inductance L; one end ofthe second partial pressure resistor R₂ is connected with the other endof the first partial pressure resistor R₁ and the anode of rectifyingdiode D₁, and the other end of the second partial pressure resistor R₂is connected with a common ground point D; the cathode of the rectifyingdiode D₁ is connected with the ends of the filter and integral capacitorC₄, the release resistor R₃, and the diac D₂, respectively. The otherends of the filter and integral capacitor C₄, and the release resistorR₃ are connected with a common ground point D. The other end of the diacD₂ is connected with the ends of the filter capacitor C₅, the filterresistor R₄, the control pole of the thyristor SCR. The other ends ofthe filter capacitor C₅, the filter resistor R₄, and the cathode of thethyristor SCR are also connected with a common ground point D. The anodeof the thyristor SCR is connected with the cathode of the clamping diodeD₃, and then is connected with a power supply end V_(DC) by a resistorR₅. The anode of the clamping diode D₃ is connected with one end of thecontrol winding T_(1D) of an oscillatory coil of a self-excitationhalf-bridge series resonant circuit. The other end of the controlwinding T_(1D) is connected with a common ground point D.

In the protection circuit of the present invention, the abnormal signalsingle-channel sampling loop is composed of a DC block capacitor C₃, afirst partial pressure resistor R₁ and a second partial pressureresistor R₂ in series which is parallel between a loading point A of oneend of a filament and a common ground point D. Through DC blockcapacitor C₃, the abnormal signal shall be applied to pressure a dividerformed by the first partial pressure resistor R₁ and the second partialpressure resistor R₂. The rectification diode D₁, the filter andintegral capacitor C₄, and the release resistor R₃ are formed into ahalf-wave peak filter to fulfill the treatment of the pressure dividersignal from the first partial pressure resistor R₁ and the secondpartial pressure resistor R₂. At the same time, the first partialpressure resistor R₁ and the filter and integral capacitor C₄ are alsoformed into an integral circuit so as to ensure the sending ofprotective signal on the electronic ballast after preheating starts. Therelease resistor R₃ provides the discharge loop of the filter andintegral capacitor C₄. The diac D₂ completes its control over thequality of abnormality signals. When the abnormality signal reaches thepre-determined value, the diac D₂ outputs the voltage to the controlpole of a thyristor SCR and activates it to be conductive. The filterresistor R₄ and a filter capacitor C₅ form a filter network to avoid thewrong action of the thyristor SCR. The clamping diode D₃ shall shortcircuit the control winding T_(1D) when the thyristor SCR turns on inorder to stop the actuation of two oscillatory windings T_(1B) andT_(1C) of the self-excitation half-bridge series resonant circuit, thuscompleting the protective action.

According to the present invention, the control winding T_(1D) is usedto control two oscillatory windings T_(1B) and T_(1C) of theself-excitation half-bridge series resonant circuit to stop oscillatingafter normalizing the abnormal signals of over-current, over-voltage andlamp rectification state from the lamp output circuit to fulfill theprotective action.

The theoretical principle of the present invention is further describedin more detail by reference to the attached drawings.

As a further improvement according to the present invention, the controlwinding T_(1D) is conjugated with the two oscillatory windings T_(1B)and T_(1C) of the self-excitation half-bridge series resonant circuit.The control winding T_(1D) shall be an auxiliary winding of thementioned the two oscillatory windings T_(1B) and T_(1C) of theself-excitation half-bridge series resonant circuit.

Furthermore, the present invention provides a single-channelcomprehensive protection circuit for a self-excitation half-bridgeseries resonant circuit having a multi-lamps output, which includes manysampling circuit units of similar structures and corresponding multiplerectifying diodes. Each of the sampling circuit units includes one DCblock capacitor and two partial pressure resistors, characterized inthat one end of the DC block capacitor is connected with the firstpartial pressure resistor, and other end of the DC block capacitor isconnected with the loading point of one end of a fluorescent lightfilament. The other end of the filament is connected with a resonantinductance. The end of the second partial pressure resistor is connectedwith the other end of the first partial pressure resistor and the anodeof the corresponding rectifying diode. The other end of the secondpartial pressure resistor is connected with a common ground point D. Thecathode of the rectifying diode is connected with the ends of a filterand integral capacitor C₄, a release resistor R₃, and a diac D₂. Theother ends of the filter and integral capacitor C₄ and the releaseresistor R₃ are connected with a common ground point D. The other end ofthe diac D₂ is connected with the ends of the filter capacitor C₅, afilter resistor R₄, and the control pole of a thyristor SCR. The otherends of filter capacitor C₅, the filter resistor R₄, and the cathode ofthe thyristor SCR are also connected with a common ground point D. Theanode of the thyristor SCR is first connected with the cathode of aclamping diode D₃, then connected with a power supply end V_(DC) througha resistor R₅. The anode of the clamping diode D₃ is connected with oneend of the control winding T_(1D) of an oscillatory coil of theself-excitation half-bridge series resonant circuit. The other end ofcontrol winding T_(1D) is connected with a common ground point D.

The theory of the above design is the same as the single-channelcomprehensive protection circuit of a self-excitation half-bridge seriesresonant circuit having a single-lamp output. So long as the abnormalsituation exists at any lamp tube, the protection circuit will makeimmediately after the corresponding sampling circuit unit receives thisabnormal signal.

The present invention provides a single-channel comprehensive protectioncircuit of a separate-excitation half-bridge series resonant circuit ofa single-lamp output, including a DC block capacitor C₃, a first partialpressure resistor R₁, a second partial pressure resistor R₂, arectifying diode D₁, a filter and integral capacitor C₄, a releaseresistor R₃, a diac D₂, a filter capacitor C₅ and a filter resistor R₄,characterized in that one end of the DC block capacitor is connectedwith the first partial pressure resistor R₁, and the other end of the DCblock capacitor C₃ is connected with a loading point A at one end of thefluorescent light filament. The other end of the filament is connectedwith a resonant inductance L. One end of the second partial pressureresistor R₂ is connected with the other end of the first partialpressure resistor R₁ and the anode of the rectifying diode D₁. The otherend of the second partial pressure resistor R₂ is connected with acommon ground point D. The cathode of the rectifying diode D₁ isconnected with the ends of the filter and integral capacitor C₄, therelease resistor R₃, and the diac D₂, respectively. The other ends ofthe filter and integral capacitor C₄ and release resistor R₃ areconnected with the common ground point D. The other end of diac D₂ isconnected with the filter capacitor C₅, the filter resistor R₄, theselected end CS of the separate-excitation half-bridge series resonantcircuit of the drive chip. The other end of the filter capacitor C₅ andthe filter resistor R₄ are also connected with the common ground pointD.

In the protection circuit of the present invention, the abnormal signalsingle-channel sampling loop is composed of a DC block capacitor C₃, afirst partial pressure resistor R₁ and a second partial pressureresistor R₂ in series connection, and then connected parallel betweenthe loading point A of one end of the filament and the common groundpoint D. Through the DC block capacitor C₃, the abnormal signal isapplied to pressure a divider formed by the first partial pressureresistor R₁ and the second partial pressure resistor R₂. The rectifyingdiode D₁, the filter and integral capacitor C₄, and the release resistorR₃ form a half-wave peak filter to process the pressure divider signalfrom the first partial pressure resistor R₁ and second partial pressureresistor R₂. At the same time, the first partial pressure resistor R₁and the filter and integral capacitor C₄ form an integral circuit toensure the sending of protective signal after the preheating start ofthe electronic ballast. The release resistor R₃ supplies the dischargeloop of the filter and integral capacitor C₄. The diac D₂ completes thecontrol of abnormal signal quantity. When the abnormal signal reachesthe set value, it outputs the voltage to the selected end CS of aseparate-excitation half-bridge series resonant circuit of the drivechip IC and the drive chip IC stops the drive output.

Furthermore, the present invention provides a single-channelcomprehensive protection circuit of a separate-excitation half-bridgeseries resonant circuit having a multi-lamp output, which includes manysampling circuit units of similar structures and their correspondingmulti-rectifying diodes. Each of the sampling circuit units includes oneDC block capacitor and two partial pressure resistors. Thecharacteristics of the circuit are that one end of the DC blockcapacitor is connected with a first partial pressure resistor, and theother end of the capacitor is connected with a loading point of one endof the fluorescent lamp filament. The other end of the filament isconnected with a resonant inductance. An end of the second partialpressure resistor is connected with the other end of the first partialpressure resistor and the anode of the rectifying diode. The end of thesecond partial pressure resistor is connected with a common ground pointD. The cathode of the rectifying diode is connected with the ends of afilter and integral capacitor C₄, a release resistor R₃, a diac D₂,respectively. The other ends of the filter and integral capacitor C₄ andthe release resistor R₃ are connected with a common ground point D. Theother end of the diac D₂ is connected with a filter capacitor C₅, afilter resistor R₄, and the selected end SC of drive chip IC for aseparate-excitation half-bridge series resonant circuit, respectively.The other end of the filter capacitor C₅ and the filter resistor R₄ isconnected with a common ground point D.

The theory of the above design is the same as a single-channelcomprehensive circuit of a separate-excitation half-bridge seriesresonant circuit of a single-lamp output. If the abnormal situationexists at any lamp tube, the protection circuit respond immediatelyafter the corresponding sampling circuit unit receives this abnormalsignal.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall be further described in combination with theattached drawings and practice examples.

FIG. 1 is a block diagram of an electronic ballast of an existingprotection circuit.

FIG. 2 is a block diagram of an electronic ballast of a single-channelprotection circuit according to the present invention.

FIG. 3 is a schematic diagram of a self-excitation half-bridge seriesresonant circuit according to the present invention.

FIG. 4 is a schematic diagram of separate-excitation half-bridge seriesresonant circuit according to the present invention.

FIG. 5 is a schematic diagram of a self-excitation half-bridge seriesresonant circuit of multi-lamp according to the present invention.

FIG. 6 is a schematic drawing of a separate-excitation series resonantcircuit of a multi-lamp according to the prevent invention.

FIG. 7 is a potential vector diagram of relevant points of lamp outputcircuit of the present invention.

FIG. 8 is a wave-form diagram of stationary lamp voltage V_(C) of thepresent invention.

FIG. 9 is a wave-form diagram of stationary voltage V_(E) of the presentinvention.

FIG. 10 is a wave-form diagram of leakage voltage V_(E) of the presentinvention.

FIG. 11 is a wave-form diagram of lamp tube over-voltage V_(E) of thepresent invention.

FIG. 12 is a wave-form diagram of reverse lamp tube rectification statevoltage V_(E) of the present invention.

FIG. 13 is a wave-form of forward lamp tube rectification state voltageV_(E) of the present invention.

FIG. 14 is a wave-form of lamp tube leakage voltage V_(C4) of thepresent invention.

FIG. 15 is a wave-form of lamp tube rectification state or over-voltageV_(C4) of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a block diagram of an electronic ballast of an existingprotection circuit. It consists of a power supply input part, a DC/ACinverter, a lamp output part and a multi-channel detection protectionand control circuit. The multi-channel, detection protection and controlcircuit includes an over-current detection circuit, an over-voltagedetection circuit and an end of lamp life detection circuit. Each of thedetection circuits takes a sample at different sampling points.Therefore, the circuit is very complex. These have been mentioned inprevious paragraphs and will not be repeated again.

FIG. 2 shows the block diagram of an electronic ballast of asingle-channel protection and control circuit of the present invention.It consists of a power supply input part, a DC/AC inverter, a lampoutput part and a single-channel protection and control circuit. Thepower supply input part generally has a DC output by means of a filterfor eliminating high frequency electromagnetic interference and arectification circuit and filter circuit. A passive or active powerfactor calibrating circuit may also be added. The DC/AC invertertransforms a DC voltage from the power supply input circuit into a highfrequency AC voltage. The lamp output part drives fluorescent lamp bythe high frequency AC square wave voltage from the DC/AC inverterthrough a LC resonance. The single-channel protection and controlcircuit is designed for increasing the reliability of the electronicballast to ensure that the electronic ballast is not damaged under theabnormal condition.

FIG. 3 shows a single-channel comprehensive protection circuit of aself-excitation half-bridge series resonant circuit having a single-lampoutput, which includes a DC block capacitor C₃, a first partial pressureresistor R₁, a second partial pressure resistor R₂, a rectifying diodeD₁, a filter and integral capacitor C₄, a release resistor R₃, a diacD₂, a filter capacitor C₅ and a filter resistor R₄, a thyristor SCR, aclamping diode D₃ and a control winding T_(1D). One end of the DC blockcapacitor C₃ is connected with the first partial pressure resistor R₁,and its other end is connected with a loading point A of the fluorescentlamp filament. The other end of the filament is connected with aresonant inductance L. One end of the second partial pressure resistorR₂ is connected with the other ends of the first partial pressureresistor R₁ and the anode of rectifying diode D₁. The other end of thesecond partial pressure resistor R₂ is connected with a common groundpoint D. The cathode of the rectifying diode D₁ is connected with theends of the filter and integral capacitor C₄, the release resistor R₃,and the diac D₂, respectively. The other ends of the filter and integralcapacitor C₄, and the release resistor R₃ are connected with a commonground point D. The other end of the diac D₂ is connected with one endsof the filter capacitor C₅, the filter resistor R₄, the control pole ofa thyristor SCR, respectively. Other ends of the filter capacitor C₅ andfilter resistor R₄ and the cathode of the thyristor SCR are connectedwith a common ground point D. The anode of the thyristor SCR isconnected with the cathode of the clamping diode D₃, and then isconnected with the power supply end V_(DC) by resistor R₅. The anode ofthe clamping diode D₃ is connected with one end of the control windingT_(1D) of an oscillatory coil of the self-excitation half-bridge seriesresonant circuit. The other end of the control winding T_(1D) isconnected with a common ground point D. The control winding T_(1D) isthe secondary winding of the oscillatory coil T_(1B) and T_(1C) of theself-excitation half-bridge series resonant circuit.

FIG. 4 shows a single-channel comprehensive protection circuit of aseparate-excitation half-bridge series resonant circuit having asingle-lamp output, including a DC block capacitor C₃, a first partialpressure resistor R₁, a second partial pressure resistor R₂, arectifying diode D₁, a filter and integral capacitor C₄, a releaseresistor R₃, a diac D₂, a filter capacitor C₅ and a filter resistor R₄,characterized in that one end of the DC block capacitor C₃ is connectedwith the first partial pressure resistor R₁, and the other end of thecapacitor is connected with a loading point A at one end of thefluorescent lamp filament. The other end of the filament is connectedwith a resonant inductance L. One end of the second partial pressureresistor R₂ is connected with the other end of the first partialpressure resistor R₁ and the anode of the rectifying diode D₁. The otherend of the second partial pressure resistor R₂ is connected with acommon ground point D. The cathode of the rectifying diode D₁ isconnected with the ends of the filter and integral capacitor C₄, therelease resistor R₃, the diac D₂, respectively. The other ends of thefilter and integral capacitor C₄, and the release resistor R₃ areconnected with a common ground point D. The other end of the diac D₂ isconnected with the filter capacitor C₅, the filter resistor R₄, aselected end CS of the separate-excitation half-bridge series resonantcircuit of a drive chip, respectively. The other end of filter capacitorC₅ and the filter resistor R₄ are also connected with the common groundpoint D.

FIG. 5 shows a single-channel comprehensive protection circuit of aself-excitation half-bridge series resonant circuit having a multi-lampoutput, including many sampling circuit units of similar structures andtheir corresponding multi-rectifying diodes D₁₋₁, D₁₋₂, . . . , D_(1-n).Each of the sampling circuit units includes one DC block capacitorsC₃₋₁, C₃₋₂, . . . , C_(3-n) and two partial pressure resistors. The endsof the DC block capacitors C₃₋₁, C₃₋₂, . . . , C_(3-n) are connectedwith the first partial pressure resistors R₁₋₁, R₁₋₂, . . . , R_(1-n),and their other ends of the capacitors are connected with loading pointsA₋₁, A₋₂, . . . , A_(-n) of one end of the relevant fluorescent lampfilament. The other end of the filament is connected with correspondingresonant inductances L₋₁, L₋₂, . . . , L_(-n). The ends of the secondpartial pressure resistors R₂₋₁, R₂₋₂, . . . , R_(2-n) are connectedwith the other ends of the first partial pressure resistors R₁₋₁, R₁₋₂,. . . , R_(1-n) and corresponding anodes of the rectifying diode D₁₋₁,D₁₋₂, . . . , D_(1-n) and their other ends are connected with a commonground point D. The cathodes of the rectifying diodes D₁₋₁, D₁₋₂, . . ., D_(1-n) are connected with ends of the filter and integral capacitorC₄, and the release resistor R₃, the diac D₂, respectively. The otherends of the filter and integral capacitor C₄ and the release resistor R₃are connected with a common ground point D. The other end of the diac D₂is connected with the filter capacitor C₅, the filter resistor R₄, andthe control pole of the thyristor SCR, respectively. The other ends ofthe filter capacitor C₅, the filter resistor R₄, and the cathode of thethyristor SCR are also connected with a common ground point D. The anodeof the thyristor SCR is connected with the cathode of the clamping diodeD₃, and then is connected with a power supply end V_(DC) through theresistor R₅. The anode of the clamping diode D₃ is connected with oneend of the control winding T_(1D) of an oscillatory coil of aself-excitation half-bridge series resonant circuit. The other end ofthe control winding T_(1D) is connected with a common ground point D.The control winding T_(1D) is the secondary winding of the oscillatorycoil T_(1B) and T_(1C) of the self-excitation half-bridge seriesresonant circuit.

FIG. 6 shows a single-channel comprehensive protection circuit of aseparate-excitation half-bridge series resonant circuit of a multi-lampoutput, including many sampling circuit units of similar structures andtheir corresponding multi-rectifying diodes D₁₋₁, D₁₋₂, . . . , D_(1-n).Each of the sampling circuit units includes one DC block capacitorsC₃₋₁, C₃₋₂, . . . , C_(3-n) and two partial pressure resistors. The endsof the DC block capacitors C₃₋₁, C₃₋₂, . . . , C_(3-n) are connectedwith the first partial pressure resistors R₁₋₁, R₁₋₂, . . . , R_(1-n),and the other ends are connected with loading points A₋₁, A₋₂, . . . ,A_(-n) of one end of a relevant fluorescent lamp filament. The other endof the filament is connected with corresponding resonant inductancesL₋₁, L₋₂, . . . , L_(-n). The ends of the second partial pressureresistors R₂₋₁, R₂₋₂, . . . , R_(2-n) are connected with the other endsof the first partial pressure resistors R₁₋₁, R₁₋₂, . . . , R_(1-n) andcorresponding the anodes of the rectifying diodes D₁₋₁, D₁₋₂, . . . ,D_(1-n) and the other ends of the second partial pressure resistors areconnected with a common ground point D. The cathodes of the rectifyingdiodes D₁₋₁, D₁₋₂, . . . , D_(1-n) are connected with the ends of thefilter and integral capacitor C₄, the release resistor R₃, and the diacD₂, respectively. The other ends of the filter and integral capacitor C₄and the release resistor R₃ are connected with a common ground point D.The other end of the diac D₂ is connected with the filter capacitor C₅,the filter resistor R₄ and the selected end CS of a separate-excitationhalf-bridge series resonant circuit of a drive chip, respectively. Theother ends of the filter capacitor C₅ and the filter resistor R₄ areconnected with a common ground point D.

The present invention integrally processes the abnormal signals forover-current, over-voltage from a lamp output circuit and end of lamplife state by using a loading point A at one end of the filament as theintegral sampling point for abnormal signals, and controlling twooscillatory windings T_(1B) and T_(1C) of the self-excitationhalf-bridge series resonant circuit through controlling winding T_(1D)to stop oscillation or controlling a selected end CS of a drive chip ICfor a separate-excitation half-bridge series resonant circuit to makethe drive chip IC stop oscillating output in order to completeprotection action.

The principle based on a loading point A at one end of filament as anintegral sampling point for abnormal signal is described in theory byreference to FIG. 7.

In FIG. 7, the meaning of various symbols are follows:

-   -   : Potential vector of B point to ground    -   : Potential vector of A point to ground    -   : Potential vector of two ends of lamp tube    -   : Potential vector of E point to ground    -   : Potential vector of two ends of DC block capacitor C₃

$\begin{matrix}{{{Evidently}\text{:}\mspace{11mu} V_{E}^{2}} = {V_{B}^{2} + \left( {V_{C} - V_{C\; 3}} \right)^{2}}} & (1) \\{{V_{C}^{2} = {V_{A}^{2} - V_{B}^{2}}}{{{Assume}\mspace{14mu}{\overset{\rightharpoonup}{V_{E}}}} = {\overset{\rightharpoonup}{V_{C}}}}} & (2) \\{{{Then}\text{:}\mspace{11mu} V_{C\; 3}} = {V_{C} - \sqrt{V_{C}^{2} - V_{B}^{2}}}} & (3)\end{matrix}$

-   -   By (1) and (2), it can be obtained that        V _(B) ²+(V _(C) −V _(C3))² =V _(A) ² −V _(B) ²  (4)

In order to prove that formula (4) is correct, it is extended asfollows:V _(B) ² +V _(C) ²−2V _(C) *V _(C3) +V _(C3) ² =V _(A) ² −V _(B) ²  (5)

-   -   (2) and (3) are added into (5) to obtain

$V_{B}^{2} = {\left. {{2\sqrt{V_{A}^{2} - V_{B}^{2}}*\left( {\sqrt{V_{A}^{2} - V_{B}^{2}} - \sqrt{V_{A}^{2} - {2V_{B}^{2}}}} \right)} - \left( {\sqrt{V_{A}^{2} - V_{B}^{2}} - \sqrt{V_{A}^{2} - {2V_{B}^{2}}}} \right)^{2}}\Leftrightarrow V_{B}^{2} \right. = {\left. {{2\sqrt{V_{A}^{2} - V_{B}^{2}}*\left( {\sqrt{V_{A}^{2} - V_{B}^{2}} - \sqrt{V_{A}^{2} - {2V_{B}^{2}}}} \right)} - \left( {V_{A}^{2} - V_{B}^{2} + V_{A}^{2} - {2V_{B}^{2}} - {2\sqrt{V_{A}^{2} - V_{B}^{2}}*\sqrt{V_{A}^{2} - {2V_{B}^{2}}}}} \right)}\Leftrightarrow V_{B}^{2} \right. = {\left. {{2V_{A}^{2}} - {2V_{B}^{2}} - {2\sqrt{V_{A}^{2} - V_{B}^{2}}*\sqrt{V_{A}^{2} - {2V_{B}^{2}}}} - {2V_{A}^{2}} + {3V_{B}^{2}} + {2\sqrt{V_{A}^{2} - V_{B}^{2}}*\sqrt{V_{A}^{2} - {2V_{B}^{2}}}}}\Rightarrow{Left} \right. = {\left. {right}\Rightarrow{\overset{\rightharpoonup}{V_{E}}} \right. = {{\overset{\rightharpoonup}{V_{C}}}.}}}}}$Therefore, the original assumption is correct. The above proves that

${\overset{\rightharpoonup}{V_{E}}} = {\overset{\rightharpoonup}{V_{C}}}$

Therefore, by a single-channel comprehensive sampling of A point asshown in FIG. 3 or FIG. 4, the E point voltage in the circuit is thevoltage of two ends of lamp tube.

The expression of the point E voltage after the current goes through thevoltage divider is as follows:V _(R2) =V _(E) *R ₁/(R ₁ +R ₂)

The expression of the voltage after the current goes through the peakvalue filter formed by D₁, C₄ and R₃ is as follows:

$\begin{matrix}{V_{C\; 4} = {\sqrt{2}V_{R\; 2}}} \\{= {\sqrt{2}V_{E}*{R_{1}/\left( {R_{1} + R_{2}} \right)}}}\end{matrix}$

Because V_(C) lamp tube voltage=V_(E)So V _(C4)=√{square root over (2)}*R ₁/(R ₁ +R ₂)*V _(C)

When the fluorescent lamp tube leaks or cannot be activated, the outputcircuit is at a resonant state, V_(E) (FIG. 10) shall be higher than thevoltage in the steady state (FIG. 9). The single-channel comprehensiveprotection circuit will detect the abnormal signal V_(E) at A point,said signal is being divided by the first partial pressure resistor R₁and the second partial pressure resistor R₂, rectified by the rectifyingdiode D₁, the filter and integral capacitor C₄, and the release resistorR₃, delayed by the first partial pressure resistor R₁ and the filter andintegral capacitor C₄ (FIG. 14). Then, the executing component will beactivated by the diac D₂ to achieve the protection.

When the fluorescent lamp tube electronic powder symmetrically ages orslowly leaks, the lamp voltage in the output circuit can be slowlyincreased; V_(E) (FIG. 11) will be higher than the voltage in the steadystate (FIG. 9). After the abnormal signal is divided, rectified anddelayed (FIG. 15), the executing component will be activated by the diacD₂ to achieve the protection.

When the fluorescent lamp tube appears the end of the lamp life state,V_(C) can produce an asymmetrical wave, the DC voltage reflected at Bpoint may be moved up and down in a parallel direction. However, aftergoing through the DC block capacitor C₃, the abnormal signal V_(E)(FIGS. 12 and 13) of forward and reverse phases with equal peak andincreased peak is obtained. This signal is gradually deepens along withapproach of the end of lamp life states and then is slowly higher thanthe voltage at the steady state (FIG. 9). After the abnormal signal isdivided, rectified and delayed (FIG. 15), the execution component willbe activated by the diac D₂ to achieve the protection.

In summary, because the sampling method of one loading point A at thefluorescent lamp filament (near one end of the resonant inductance L) isused, the present invention integrally processes the abnormal signalsfor over-current, over-voltage and lamp tube end of lamp life state. Thepresent invention replaces the circuit design of multi-channel andmulti-point sampling in the conventional technology, and achieves theobjective for simplifying the circuit, reducing the cost and space,increasing the reliability and supporting miniaturization anddevelopment of electronic lighting products.

It should be noted that the above-mentioned practice example onlydescribes the present invention, but is not limited to the invention.Any improvement or innovation not exceeding the scope of the substanceof the invention shall be deemed as being included in the scope of thepresent invention.

1. A single-channel comprehensive protection circuit for aself-excitation half-bridge series resonant circuit having a single-lampoutput, comprising a DC block a capacitor C₃, a first partial pressureresistor R₁, a second partial pressure resistor R₂, a rectifying diodeD₁, a filter and integral capacitor C₄, a release resistor R₃, a diacD₂, a filter capacitor C₅, a filter resistor R₄, a thyristor SCR, aclamping diode D₃ and a control winding T_(1D); characterized in thatone end of the DC block capacitor C₃ is connected with one end of thefirst partial pressure resistor R₁, and the other end of the DC blockcapacitor is connected with a loading point of one end of a fluorescentlamp filament; the other end of the filament is connected with aresonant inductance L; one end of the second partial pressure resistorR₂ is connected with the other end of the first partial pressureresistor R₁ and an anode of the rectifying diode D₁, and the other endof second partial pressure resistor R₂ is connected with a common groundpoint; a cathode of the rectifying diode D₁ is connected with one end ofthe filter and integral capacitor C₄, one end of the release resistorR₃, and one end of the diac D₂, respectively; the other end of thefilter and integral capacitor C₄ and the other end of the releaseresistor R₃ are connected with the common ground point; the other end ofdiac D₂ is connected with one end of the filter capacitor C₅, one end ofthe filter resistor R₄ and a control pole of the thyristor SCR,respectively; the other end of the filter capacitor C₅, the other end ofthe filter resistor R₄, and a cathode of the thyristor SCR are connectedwith the common ground point; an anode of the thyristor SCR is connectedwith a cathode of the clamping diode D₃, and is connected with an end ofa power supply end V_(DC) through a resistor R₅; an anode of theclamping diode D₃ is connected with one end of the control windingT_(1D) of an oscillatory coil of a self-excitation half-bridge seriesresonant circuit; and the other end of the control winding T_(1D) isconnected with the common ground point.
 2. The single-channelcomprehensive protection circuit according to claim 1, wherein thecontrol winding T_(1D) is conjugated with the oscillatory winding T_(1B)and T_(1C) of the self-excitation half-bridge series resonant circuit.3. The single-channel comprehensive protection circuit according toclaim 2, wherein the control winding T_(1D) is an auxiliary winding ofthe oscillatory winding T_(1B) and T_(1C) of the self-excitationhalf-bridge series resonant circuit.
 4. A single-channel comprehensiveprotection circuit for a self-excitation half-bridge series resonantcircuit having a multi-lamp output, comprising a plurality of samplingcircuit units of the same structure and their corresponding a pluralityof rectifying diodes, each of said plurality of sampling circuit unitsincluding a DC block capacitor, and a first partial pressure resistorand a second partial pressure resistor; characterized in that one end ofthe DC block capacitor is connected with the first partial pressureresistor, and other end of the DC block resistor is connected with aloading point of one end of a fluorescent light filament; the other endof the filament is connected with a resonant inductance; one end of thesecond partial pressure resistor is connected with the other end of thefirst partial pressure resistor and an anode of a correspondingrectifying diode; the other end of the second partial pressure resistoris connected with a common ground point; a cathode of the rectifyingdiode is connected with one end of a filter and integral capacitor C₄,one end of a release resistor R₃, and one end of a diac D₂,respectively; the other end of the filter and integral capacitor C₄, andthe other end of the release resistor R₃ is connected with the commonground point; the other end of the diac D₂ is connected with one end offilter capacitor C₅, one end of a filter resistor R₄, and a control poleof a thyristor SCR, respectively; the other end of the filter capacitorC₅, the filter resistor R₄, and a cathode of the thyristor SCR areconnected with the common ground point; an anode of the thyristor SCR isconnected with a cathode of a clamping diode D₃, and then is connectedwith an end of a power supply V_(DC) through a resistor R₅; an anode ofthe clamping diode D₃ is connected with one end of a control windingT_(1D) of an oscillatory coil of a self-excitation half-bridge seriesresonant circuit, and the other end of the control winding T_(1D) isconnected with the common ground point.
 5. The single-channelcomprehensive protection circuit according to claim 4, wherein thecontrol winding T_(1D) is conjugated with the oscillatory winding T_(1B)and T_(1C) of the self-excitation half-bridge series resonant circuit.6. The single-channel comprehensive protection circuit according toclaim 5, wherein the control winding T_(1D) is an auxiliary winding ofthe oscillatory winding T_(1B) and T_(1C) of the self-excitationhalf-bridge series resonant circuit.
 7. A single-channel comprehensiveprotection circuit for a separate-excitation half-bridge series resonantcircuit having a single lamp output, comprising a DC block capacitor C₃,a first partial pressure resistor R₁, a second partial pressure resistorR₂, a rectifying diode D₁, a filter and integral capacitor C₄, a releaseresistor R₃, a diac D₂, a filter capacitor C₅ and a filter resistor R₄;characterized in that one end of the DC block capacitor C₃ is connectedwith one end of the first partial pressure resistor R₁, and the otherend of the DC block capacitor is connected with a loading point of oneend of a fluorescent light filament; the other end of the filament isconnected with a resonant inductance L; one end of the second partialpressure resistor R₂ is connected with the other end of the firstpartial pressure resistor R₁ and an anode of the rectifying diode D₁ andthe other end of the second partial pressure resistor R₂ is connectedwith a common ground point; a cathode of the rectifying diode D₁ isconnected with one end of the filter and integral capacitor C₄, one endof the release resistor R₃, and one end of the diac D₂, respectively;the other end of the filter and integral capacitor C₄ and the other endof the release resistor R₃ are connected with the common ground point;the other end of the diac D₂ is connected with one end of the filtercapacitor C₅, one end of the filter resistor R₄, and a selected end CSof a drive chip of the separate-excitation half-bridge series resonantcircuit, respectively; and the other end of filter capacitor C₅ and theother end of the filter resistor R₄ are connected with the common groundpoint.
 8. The single-channel comprehensive protection circuit accordingto claim 7, characterized in that the drive chip stops the oscillatoryoutput when the electric potential to the common ground point of theselected end CS of drive chip IC is higher than 0.6V.
 9. Asingle-channel comprehensive protection circuit for aseparate-excitation half-bridge series resonant circuit having amultiple-lamp output, comprising a plurality of sampling circuit unitsof the same structure and their corresponding a plurality of rectifyingdiodes; each of said plurality of sampling circuit units including a DCblock capacitor, a first partial pressure resistor and a second partialpressure resistor; characterized in that one end of the DC blockcapacitor is connected with the first partial pressure resistor, and theother end of the DC block capacitor is connected with a loading point ofone end of a fluorescent lamp filament; the other end of the filament isconnected with a resonant inductance; one end of the second partialpressure resistor is connected with the other end of the first partialpressure resistor and an anode of a corresponding rectifying diode; theother end of the second partial pressure resistor is connected with acommon ground point; a cathode of the rectifying diode is connected withone end of a filter and integral capacitor C₄, one end of a releaseresistor R₃, one end of a diac D₂, respectively; the other end of thefilter and integral capacitor C₄, and other end of the release resistorR₃ are connected with the common ground point; the other end of the diacD₂ is connected with one end of a filter capacitor C₅, one end of afilter resistor R₄, and a selected end SC of a drive chip for theseparate-excitation half-bridge series resonant circuit, respectively;and the other end of the filter capacitor C₅ and the filter resistor R₄are connected with the common ground point.